Generally in such electric door openers the unlocking and/or locking position of the swivel latch is determined by the position of the locking lever. When current is applied to the electromagnet, the safety lever holding the locking lever is activated and adjusted such that it unlocks the locking lever and thus unlocks the swivel latch. Furthermore, as an additional measure it is known to secure the safety lever with a second safety lever that is uncoupled from the above-mentioned safety lever in order to avoid an unwanted adjustment of the first safety lever into an unlocking position of the swivel latch and/or of the locking lever.
DE 19707759 C1 describes a locking/unlocking device with an arrangement of two aforesaid safety levers, wherein the second safety lever secures the first safety lever. An electromagnet is provided for controlling both the safety levers. The second safety lever that is mechanically uncoupled from the first one is in active connection with one end of the electromagnet by magnetic coupling and can be adjusted from a position locking the first safety lever into a position unlocking the safety lever. A pin that is extendable from the coil body of the electromagnet is provided at the other end of the electromagnet for the adjustment of the first safety lock. When current is applied to the coil of the electromagnet, the coil core is magnetized and drawn into the coil and thereby the second safety lever magnetically coupled to it swivels. At the same time the coil pin at the other end of the coil is moved out of the coil and this leads to a swiveling of the first safety lever into the unlocking position. The door opener is in an unlocking position if the first arm of the first safety lever is no longer in mesh with the locking lever and a torsion of the prestressed locking lever can take place as a result. In order to enable the return of both the safety levers to their locking position after current is no longer applied to the electromagnet, compression springs are provided between the housing wall of the door opener and one of the arms of each safety lever.
This and other known locking/unlocking devices with impact safety have many, partly filigree components that are expensive to manufacture and install.